I started the seeds for this Winter Density (from Pinetree) at the very end of November, so six weeks from sowing. You can see Red Sails next to it. Red Sails grows prolifically, and is a first-rate cut lettuce. But it gets banged up like nothing else in a heavy rainstorm; I've had to pinch it back severely to deal with damaged leaves. The Winter Density, on the other hand, is much sturdier.